Wanting Child custody after abuse and negligence from Father

My husband and I separated 2003. We have a son whom I left with him and his Family for I was still not settled at that time. I saw him every so often for The Aunt(husband's sister) would always tell me my son is busy with school.It really hurt me to feel that I was losing my son to them. I would always text my husband wanting to arrange Proper and ample visitation time but he would always have no time.Now my son is with me for Summer vacation. He is now 10 years old. We have talked about his wanting to stay with me more. So, I told him that he'll finish Elementary first then I'll open it up to his Dad. That's when he told me while crying that he didn't want to go home anymore. I was disturbed and probed. He told me about his Aunt pulling his hair(sabunot) and pinching his ears(pingot) whenever he does something wrong. The reasons he stated were because of mistakes while reviewing for school! I was deeply hurt and angered and right there and then decided to keep him with me. I am a Work-at-home Mom so I do spend more of my time at home. I have a new partner now with a 5-yr.old daughter. My partner has known about my past relationship from the start, which was 2006. My husband is also aware because there would be times that it is the two of them who would see each other for the picking up/bringing back of our son. My husband is very busy. He barely has time for our son. He may be earning a lot but I know that he is still supporting his Mother and jobless sister. With the physical hurting of our son, he was forced to talk with me for I already told him that our son will not go back to that house. He insists that he will just move out, get an apartment and a maid so that our son will stay with him without fear of being hurt again. My questions:
1) What is the chance of my lawfully keeping custody of our son considering the situation?
2) What legal action should I take against the Aunt who has hurt my child?

you can file a case of child abuse against the aunt.

if you are still living in with another man, you'll have a weaker chance of keeping your kids.